Understanding Light Energy and Waves

Light Energy

• Light energy is produced when electrons jump to a higher energy level after absorbing energy and then release light when falling back to a lower energy level.
• This released energy is in the form of photons, bundles of energy packages.

Electromagnetic Waves

• Light travels at 300,000 km/sec (186,000 mi/sec) in a vacuum.
• Light travels slower in other mediums such as air, water, and glass.

Light as a Transverse Wave

• Light's energy is perpendicular to its direction of motion.
• Moving photons generate electric and magnetic fields.

Electromagnetic Spectrum

• The visible spectrum is the portion of the electromagnetic spectrum that humans can see.
• The colors of visible light are red, orange, yellow, green, blue, indigo, and violet (ROY G. BIV).
• The wavelengths range from longest to shortest, infrared to ultraviolet light.

Refraction of Light

• Refraction is the bending of light due to a change in speed.
• The index of refraction measures how much a material refracts light.
• Prisms are transparent materials (e.g., glass) that bend light, separating it into different colors due to differences in wavelengths.

How We See

• The lens in our eyes refracts light to focus it onto the retina.
• Nerves then transmit the image to the optic nerve and the brain.
• Rods are light-sensitive nerve cells enabling us to see light and dark.
• Cones are nerve cells helping us to see color and light.

Color of Light

• Transparent objects transmit light; the transmitted color is the color we see. Other colors are absorbed.
• Translucent objects scatter and transmit light.
• Opaque objects reflect or absorb light; the reflected color is the object's color.

Color of Objects

• White light contains all colors of the visible spectrum.
• Black objects absorb all colors and reflect no light.

Primary Colors of Light

• Red, blue, and green are primary colors of light.
• Mixing these colors can produce other colors.

Secondary Colors of Light

• Secondary colors of light are created by combining two primary colors.
• Examples include magenta, cyan, and yellow.

Paint Pigments

• Paint pigments are colored substances that absorb or reflect light, giving color to materials.
• Red, yellow, and blue are the primary pigments.
• Mixing these pigments subtracts colors from the light to create different colors.

Pencil Demonstration

• A pencil appears bent or broken when viewed in water due to the refraction of light.

Rainbow

• A rainbow is formed when sunlight is refracted, reflected, and refracted again inside water droplets.
• The different colors separate because of differences in how much different colors bend in water.

Color Blindness

• Some people have a problem with their color receptors (cones).
• This can impact their ability to distinguish certain colors.
• Red-green color blindness is a common type.

Reflection Diagram

• The angle of incidence equals the angle of reflection when light reflects off a surface.
• The incident beam strikes a mirror, and the reflected beam bounces off it.
• A normal line is drawn perpendicular to the surface of the mirror.

Law of Reflection

• The angle of incidence is equal to the angle of reflection.

Diffraction

• Diffraction is the bending of waves around the edge of a barrier.
• The original wavefronts are altered into new wavefronts.

Diffraction Grating

• Each space between ruled grooves in a diffraction grating acts as a slit.
• Light bends around the edges and gets refracted as it passes through the slits.

Sources of Light

• Incandescent light is produced by heating an object until it glows.
• Fluorescent light is produced by electron bombardment of gas molecules.

Optical Instruments

• Examples include cameras, telescopes, microscopes, lasers, and fiber optics.

Lasers

• Lasers are an acronym for Light Amplification by Stimulated Emission of Radiation.
• Laser light is coherent; all the waves have equal wavelengths and are in phase.
• This makes it potent and concentrated.
• Holography uses lasers to create 3D images.
• Fiber optics use lasers to transmit light through fibers of glass or plastic for communication, medicine, etc.